The invention relates to a process for removing or separating pollutants, such as sulphur or metal compounds from SO.sub.2 -containing flue or other waste gases by contacting the latter with aqueous binder suspensions.
The problem of economically removing pollutants from flue and other waste gases has not hitherto been solved. Although there are numerous processes for the selective removal of sulphur dioxide from flue gases, such as a process involving washing with a sodium sulphite solution or with aqueous ammonia solutions at 60.degree. to 70.degree. C. and subsequent thermal regeneration, as well as processes involving washing with dilute sulphuric acid or with calcium sulphite solutions, they suffer from the disadvantage that the contacting solutions used require considerable expenditure for apparatus, due to their corrosive properties. The also known dry sorption processes, e.g. according to Austrian Pat. No. 283,289, in which specially produced, usually hydroxidic absorption materials are used, which materials are regenerated following sulphur absorption and which have to be moved backwards and forwards whilst involving considerable transportation costs between the absorption point, e.g. the power station, and the regeneration point, e.g. a sulphuric acid plant, are also complicated and therefore uneconomical, especially because considerable quantities of coke are required for roasting purposes.
A fundamental disadvantage of these processes, which have essentially been proposed for fuel or flue gas desulphurization is that they fail to remove other pollutants, such as heavy metals present in the waste gas.
In addition, DE-OS No. 2,237,929 discloses a process for using biomass for removing gaseous organic waste gases or at least waste gases containing organic constituents. Activated sewage sludge can be used as the biomass, so that the organic pollutants in the waste gases, such as occuring the foodstuffs industry, are degraded via the metabolism of microorganisms.
Finally, it is known from DE-OS No. 2,248,256 to filter spent air, biologically activated humificated substances being used as the solid filter material.
The problem of the present invention is to eonomically remove or separate pollutants from waste gases using a process of the aforementioned type, whilst not being limited solely to desulphurization, but instead effectively removing other solid, liquid and gaseous pollutants, such as toxic substances. Moreover, the sorbent used for binding the pollutants is to be in the form of a product, which is itself a valueless waste product to be eliminated, i.e. it is inexpensive and ready to use, whilst involving much lower preparation and transportation costs. Finally, it not only permits desulphurization, but also the elimination of other pollutants and can make them available again in regenerated form. In addition, roasting is to take place in a more economic manner.